14 PROCEEDINGS OF THE ACADEMY OF 



tions to the members at some future time, but at present wished only to direct 

 their attention to a portion of a trunk of Yucca alafolia, Avhich lie exhibited, 

 the structure of which he suggested could not be accounted for on any theory 

 generally known. The general idea was that the sap of plants ascended through 

 the system, and was elaborated in the leaves, where the woody matter was 

 formed, and afterwards descended, in exogenous plants forming a regular con- 

 centric layer over the last year's wood, and in endogenous structures returning 

 by the interior, pushing these descending columns of wood through the mass 

 of cellular matter without order or system. 



It would be seen that in this endogenous Yucca the woody matter, if it ever 

 descended at all, as our present belief demanded it should do, had descended in 

 a very regular and beautiful manner, quite as systematic, in fact, as most exo- 

 gens would do. The wood was arranged in annual rings, not entirely con- 

 centric ; but some tropical exogens did not have the woody annual layers al- 

 ways forming an entire circle any more than in this. In this case the annual 

 layers of wood extended about two-thirds of the distance round the axis, and 

 such layer was about the eighth of an inch thick. These annual layers were 

 made visible by the bundles of fibres being packed more closely together to- 

 wards the end of the season's growth, just as they are in exogens, from which, 

 indeed, there was very little to distinguish this structure on a cursory exami- 

 nation but the absence of the so-called medullary rays. 



March 29th. 

 The President, Dp.. Ruschenberger, in the Chair. 

 Thirty members present. 



A resolution to amend Art. XI, Chapter 10 of the By-Laws by 

 the omission of the word " gratuitous," was adopted after a third 

 reading. 



The following gentlemen were elected members : 



Geo. Hewston, W. H. Eisenbrey and Alfred Tucker. 



On favorable report of the committees the following papers were 

 ordered to be published : 



Cross fertilization and the law of sex in EUPHORBIA. 

 BY THOMAS MEEHAN. 



Mr. Charles Darwin's interesting observations on cross fertilization have 

 opened a new world for original discovery. The list of plants which seem to 

 avoid self fertilization is already very large. I think Euphorbia may be added 

 to the number. Certainly'this is the case with Euphorbia fulg ens, Karw. (E. 

 Jacguinajlora, Hook.) which I have watched very closely in my greenhouse 

 this winter. Several days before the stameus burst through the involucre, 

 which closely invests them, the pistil with its ovarium on the long pedicel 

 has protruded itself beyond, exposed its stigmatic surfaces, and received the 

 pollen from the neighboring flowers. The way in which the pollen scatters 

 itself is curious. In most flowers a slight jar or a breath of wind will waft 

 the pollen to the stigmas, but I have not been able to notice any to leave the 

 flowers in this way; for as soon as the anther cells burst the whole stamen 

 falls from its filament like pedicel and either drops at once on the pistils of 

 other flowers cr scatters its pollen grains by the force of the fall. 



This Euphorbia also furnishes another contribution to the theory of sex 

 which I have advanced. The plan on which the male and female organs are 

 formed is evidently a common one; and the only reason why some flower 



[March, 



